1. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, and Center for Biomolecules and Complex Molecular Systems, Flemingovo nám. 2, 16610 Prague 6, Czech Republic, Department of Chemistry, University of California at Irvine, Irvine California 92697-2025, and Department of Physics T37, Technical University Munich, 85748 Garching, Germany